Typically, an engine cooling system has a pump to circulate coolant used to cool the engine, a radiator to cool the coolant and a bypass to allow coolant to circulate through the engine without being cooled by the radiator. In motor vehicles, a cabin heater is usually, provided so that the coolant warmed by the engine provides heating for any occupants of the vehicle. Additionally, the main engine coolant is often used to cool one or more additional heat exchangers or radiators such as a transmission oil cooler, a fuel cooler or an air-charge cooler. A temperature responsive control valve is provided to control the flow of coolant through the radiator and frequently also to control the flow of coolant through the bypass.
GB2401166A describes a temperature responsive flow control valve in which a housing has a hot inlet for connection to a bypass receiving hot coolant from an engine, a cold inlet for connection to a radiator and an outlet for a pumped return to the engine. A thermostat capsule has a pushrod which reacts against a spoked abutment and carries a flange which is a running clearance in a bore of the housing leading from the cold inlet. The capsule is carried in a valve spool having a flange with a seat which seals against the housing. When coolant in the hot inlet is below 80° C., the valve prevents flow from the hot and cold inlets and to the outlet but as the temperature rises above 80° the valve spool moves progressively towards the hot inlet to allow flow past the seat to allow flow from the hot inlet to the outlet. Further movement of the valve spool with increasing temperature at the hot inlet brings the flange out of the bore in the cold inlet to allow flow through the cold inlet past the flange.
However, the inventors herein have recognized several issues with such an approach. As one example, even though the pressure at the cold inlet is substantially the same as that at the outlet, if there is an excessive clearance between the flange and the bore in the cold inlet, there can be unwanted flow through the cold inlet even if the flange is still in the bore of the cold inlet.
Thus, in one example, the above issues may be addressed by providing a temperature responsive control valve for use in an engine cooling system where the above problem is eliminated or minimised. The temperature responsive control valve for use in an engine cooling system in which a pump circulates liquid coolant to an engine, coolant from the engine is returned to the pump through a radiator and a bypass arranged in parallel and the control valve controls flow as between the radiator and the bypass, the control valve having a housing defining a hot inlet which in use is connected to the bypass, a cold inlet which in use is connected to the radiator, an outlet which in use is connected to the pump, a first valve member to control the flow of coolant from the hot inlet to the outlet, a second valve member to control coolant flow from the cold inlet to the outlet and a temperature responsive actuator to move the first and second valve members, wherein the control valve is operable to substantially prevent coolant flow from the hot and cold inlets to the outlet when the temperature of the coolant sensed by the temperature responsive actuator is below a first predetermined temperature, to permit coolant flow only from the hot inlet to the outlet when the sensed temperature is between the first predetermined temperature and a second higher predetermined temperature and to permit coolant flow from both of the inlets to the outlet when the sensed temperature is above the second temperature, wherein the second valve member is spring biased onto a seat in the housing to prevent coolant flow from the cold inlet to the outlet when the temperature of the coolant sensed by the temperature responsive actuator is below the second predetermined temperature and is lifted from the seat by the first valve member when the temperature of the coolant sensed by the temperature responsive actuator exceeds the second predetermined temperature.
In some examples there may be a lost motion connection between the first valve member and the second valve member. A biasing spring may act between the first valve member and the second valve member.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.